Generating mechanism for tooth flank generating machines



March 24, 1970 e. R. SOMMER 3,501,869

GENERATING MECHANISM FOR TOOTH FLANK GENERATING MACHINES Filed Nov. 21,1967 2 sheets-sheet;

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m VEN TaR GE RD ROBERT .SOHMER March 24, 1970 G. R. SOMMER 3,501,869 7GENERATING MECHANISM FUR TOOTH FLANK GENERATING MACHINES Filed Nov. 21,196'? 2 Sheets-Sheet 2 Fig. 2 203 Fig.3

V NTOR GERD ROBRT50HM6Q Mltwaw $44,

United States Patent Ofl ice 3,501,869 Patented Mar. 24, 1970 US. Cl.51-54 5 Claims ABSTRACT OF THE DISCLOSURE An involute gear tooth grinderin which the gear is held stationary while the grinding wheel is swungangularly about the gear axis and simultaneously fed toward and awayfrom the gear to form the desired involute profile. The grinding wheelis slidably mounted on a swinging table and is moved on its slide by arocker fixed on the grinder slide and having an end angularly adjustablyconnected to a carriage displaceable on the table at an angle to thegrinding wheel feed direction. Movement is transmitted to the carriageby a flexible band arrangement such that angular motion of the tablecauses a linear displacement of the carriage which, in a ratio dependingon the selected angular disposition of the rocker, is translated into ashifting of the grinder slide toward and away from the gear to form thedesired profile. Preferably two swinging grinders are employedsimultaneously on difierent teeth of the gear.

The generating mechanism disclosed as including an axis and a pair ofadditional rollers, which rotatably mounted on a respective table andeach having rotatable therewith a circular segment. Each additionalroller is connected by a pair of flexible bands to the main roller insuch a manner that, upon swinging of its associated table about the axisof the main roller or cylinder, the roller on the table is rotated ineither of two angular directions depending upon the direction ofswinging of its associated table. The circular segment fixed to rotatewith each table roller is connected by a pair of flexible bands toopposite ends of a slide for moving the flank generating tool so that,upon rotation of the table roller, the slide is longitudinally displacedalong a guide. Thus, the slide is moved in either of a pair of oppositedirections in accordance with the direction of rotation of theassociated table roller corresponding to swinging or rotation in aselected direction of the table.

CROSS REFERENCE TO RELATED APPLICATION The tooth flank generatingmechanism of the present invention is an improvement on that shown anddescribed in copending application Ser. No. 555,786, filed June 7, 1966,and now abandoned by Gerd Robert Sommer for Generating Apparatus of aGear-Cutting Machine.

BACKGROUND OF THE INVENTION Three different kinds of gear tooth flankgenerating arrangements are recognized in the prior art. In onearrangement, the workpiece rolls. In a second arrangement, the workpieceis rotated in operative relation with a tangentially and rectilinearlymoving tool. In a third arrangement, tooth generation is etfected with arolling or hobbing tool. In all three cases, a tool having the shape ofa gear wheel or of a gear rack may be employed, or there may be used atool having a point generating an involute gear profile to be produced.

The prior art discloses a gear tooth flank generating arrangementincluding a continuously rotatable work table and a tool-holder tablewith rectilinear motion timed with relation to the rotation of the worktable. The tool, such as a grinding wheel, is pivotal on the tool-holdertable in such a manner as to ensure that the tool is maintainedtangentially relative to the tooth flank profile to be generated.

It is also known to provide gear tooth flank generating machines inwhich the tooth flank profile is generated machines in which the toothflank profile is generated by means of driving drums and roll bands. Inparticular, a tooth flank generating means for involute gears and havingtwo tools, such as grinding wheels, is known in which two positivelyconnected generating systems, each having a respective grinding wheel,are provided and a gen erating motion is carried out simultaneously andon two tooth flanks facing in opposite directions so that the toolssimultaneously machine symmetrical profile sections of a righthand and aletthand tooth flank on the workpiece, the workpiece not participatingin the generating mot on. In this system, two pivoting arms arerotatable or swingable about the axis of a generating cylinder disposedconcentrically to the workpiece blank and arranged to be stationary, thepivoting arms executing a rocking motion in opposite directions and eacharm being provided with a generating slide carrying a tooth flankgenerating tool such as a grinding wheel. The generating slides arerollably connected with a generating cylinder by means of rolling bands.When using such a generating device with two symmetrically rockinggrinding Wheels and including a roller band arrangement, it will benecessary to employ a corresponding driving cylinder whose diameter isidentical with the generating circle, in the case of circular gear-shapeof rack-shape tools, or with the base circle, in the case of tools whichgenerate the involute profile with a point. This necessitates the use ofa large number of highly accurate driving cylinders.

In the copending application mentioned above, a rolling drive forinvolute tooth generating machines is provided in which the workpiece onwhich an involute profile is to be shaped is stationary and the toolholder is shiftable in a longitudinal guide. This guide is disposedparallel to the imaginary straight rolling line, and on a tablerotatable about the axis of the workpiece. The tool holder is drivenfrom a stationary drive member disposed coaxial with the axis ofrotation of the table, and a drive member mounted in the table is indriving connection with the stationary drive member. The drive membermounted in the table, in turn, drives a carriage which is reciprocablerectilinearly in the table at an angle to the longitudinal extent of theguide for the tool holder. This carriage carries a rocker which isadjustable angularly with respect to the direction of its motion, and asliding block connected to the tool holder is guided in this rocker.

In one embodiment of the drive shown in the mentioned copendingapplication, the driving connection between the two drive members isestablished in that the stationary drive member, coaxial with the axisof rotation of the table, is formed with gear teeth which mesh with agear mounted on a common shaft with the drive member on the table, andwhich is driven by a motor efiecting rotation motion of the table. Thedrive member on the table, in turn, drives a threaded spindle likewisemounted rotatably in the table, and this spindle extends parallel to theguide for the carriage and engages a thread formed thereon.

SUMMARY OF THE INVENTION This invention relates to generating mechanismsfor gear tooth flank generating machines and, more particularly, to animproved and simplified generating mechanism capable of especially greatprecision in generating gear tooth flanks.

In accordance with the invention, the generating mechanism includes twodrive members in the form of cylindrical rollers and interconnected byflexible bands, one cylindrical roller being fixedly mounted on themachine base and the other cylindrical roller being rotatably mounted onthe tool-carrying table. The cylindrical roller on the tool-carryingtable is connected with a tool-supporting slide by flexible bands. Theinterconnection between the stationary roller mounted on the machinebase and the rotatable roller mounted on the table, by the flexiblebands, is such that the roller mounted on the table is positivelyrotated in opposed directions responsive to rotation of the table inopposed directions about an axis concentric with the workpiece and withthe stationary cylindrical roller.

The cylindrical roller mounted on the table preferably comprises twoseparate roller surfaces secured to a common shaft, one roller surfacecomprising a cylinder and the other roller surface comprising acylindrical segment. The cylinder roller surface is connected by twoflexible bands to opposite ends of a longitudinally and rectilinearlydisplaceable tool-supporting slide, and the cylinder segment rollersurface is connected by two flexible bands, extending in oppositedirections, to the stationary cylindrical roller.

The arrangement of the invention provides for great freedom indimensioning the various components of the rolling drive. For example,if a relatively large diameter of the stationary roller, which iscoaxial with the axis of rotation of the table, results from the overalldesign of the gear tooth flank generating machine, but if it is requiredthat the guide for the tool-supporting carriage should not beexcessively long, then provisions can be made for that part of thetable-mounted rolling surface which is connected with the stationaryrolling surface to be, for example, twice the diameter of that part ofthe table mounted roller surface connected with the toolsupportingcarriage.

Accordingly, an object of the present invention is to provide asimplified rolling drive for the tool-supporting means of a gear toothflank generating machine.

Another object of the invention is to provide such a drive by means ofwhich there may be obtained especially great precision in machining geartooth flanks.

A further object of the invention is to provide such a drive includingcircular rolling surfaces interconnected by flexible bands.

Still another object of the invention is to provide such a driveincluding two drive members, one being stationary or fixed on themachine bed and the other being rotatable on a table swingable about theaxis of the stationary member, and in which the two drive members arecylindrical rolling surfaces interconnected by flexible bands.

A further object of the invention is to provide such a drive asjust-mentioned in which the rolling surface on the table is rotatablymounted thereon and is connected with components on the table byflexible bands.

Yet, another object of the invention is to provide such a drive in whichthe drive member rotatably mounted on the table comprises two separaterolling surfaces on a common shaft, one rolling surface comprising acylinder and the other rolling surface comprising a cylindrical segment.

A further object of the invention is to provide a drive of the typejust-mentioned in which the cylinder on the table is connected with thestationary cylinder on the machine bed, and the cylindrical segment onthe table is connected with a tool-supporting carriage.

An ancillary object of the invention is to provide such a rolling drivewhich provides great freedom in dimensioning the various components ofthe drive.

l BRIEF DESCRIPTION OF THE DRAWINGS For an understanding of theprinciples of the invention, reference is made to the followingdescription of a typical embodiment thereof as illustrated in theaccompanying drawings.

In the drawings:

FIG. 1 is a front elevation view of one half of an involute gear toothgenerating machine, shown as a grinder solely by way of example,incorporating a rolling drive in accordance with the invention;

FIG. 2 is a side elevation view correspondng to FIG. 1;

FIG. 3 is a plan view, corresponding to FIG. 1, showing the parts of thegrinder in a first working position corresponding to FIG. 1; and

FIG. 4 is a view similar to FIG. 3 but illustrating a second workingposition of the parts of the grinder, corresponding with FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, aninvolute gear tooth flank grinder, serving as one example of a toothflank generating machine to which the drive of the invention is applied,is illustrated as including a circular machine bed 201 having two gearsegments 202 on its periphery and staggered with respect to each other.The axis of the gear 204 whose tooth flanks are to be generatedcoincides with a common vertical center line or axis 203 of machine bed201 and of gear segments 202. By suitable means, not shown but known tothose skillednithe lprs if gear 204 is so supported that it is rotatableby one tooth pitch only after the generation of a pair of tooth flanks,and can perform only axial motions during tooth flank generation of spurgears having teeth with straight or planar flanks. During the toothflank generation of helical spur gears, a corresponding helical motionis imparted to workpiece 204.

The aforementioned common vertical center line is the axis of a shaft203, which serves as a pivot axis for two symmetrically identical tables206, which are thus swingable about the shaft 203. While two tables 206are illustrated by way of example, the invention is not limited to agenerating machine including two tables or any specific number oftables. The upper surface of each table 206 is formed with rectilinearguide 207 in which a tool holder 208 is rectilinearly shiftable. Eachtool holder 208 carries a respective tooth flank generating tool such asa grinding wheel 209. An approach carriage 210 is provided for theadjustment of the proper starting position of the grinding wheel withrespect to the workpiece 204, and approach carriage 210 is guided intool holder 208 for horizontal movement transversely of guide 207, andpreferably at right angles to guide 207. A pivoting carriage 211 ismounted on approach carriage 210 for angular displacement about the axisof a shaft 233 which extends horizontally and which is perpendicular tothe plane of FIG. 2. Grinding wheel 208 is mounted on pivoting carriage211, and a motor (not shown) is accommodated in carriage 211 to drivegrinding wheel 209.

In order to rotate tables 206 about shaft 203, each table has a spurgear 213 rotatably mounted thereon and meshing with a respective gearsegment 202, each spur gear 203 being driven by a motor 217. Each table206 further mounts a carriage 220 which is reciprocable rectilinearly ofa rectilinear guide 220' extending at an angle relative to guide 207.Each carriage 220 carries a rocker 221 which is angularly adjustablerelative to the direction of motion of the associated carriage 220. Eachrocker 221 is formed as a longitudinal guide for a sliding block 226,and each sliding block 226 is pivotally connected to the free end of afixed arm 227 projecting from the assiciated tool holder 208.

A cylindrical roller 229 is rotatably mounted on each table 206 forrotation about a vertical axis adjacent the associated guide 220. Eachcylindrical roller 229 is connected by two flexible bands 228 and 228'to opposite ends of carriage 220. One band 228 is connected to one endof carriage 220 and extends around cylindrical roller 229 in onedirection and at a selected level thereof, and the other band 228' isconnected to the opposite end of carriage 220 and extends aroundcylindrical roller 229 in the opposite direction and at an adjacentlevel thereof. Thus, responsive to rotation of cylindrical roller 229 inopposite angular directions, carriage 220 will be reciprocated inopposite directions along guide 220' with the shifting movementprecisely controlled in accordance with the rotation of the associatedcylindrical roller 229.

Each. cylindrical roller 229 is fixed to a common shaft along with acylindrical segment 230, and each segment 230 is connected by twoflexible bands 231 and 231 to a stationary cylindrical roller 232 whichis coaxial with a common axis of rotation of tables 206. Bands 231 and231' extend in respective opposite directions relative to segment 230and stationary cylindrical roller 232, and are at adjacent levels on thesegment and on the roller 232.

The arrangement just described operates in the following manner. At thestart of machining gear 204, the two approach carriages 210 are soadjusted that the intersection formed by the flank and the outsidediameter of each gear tooth falls on an imaginary straight rolling line223 which is tangent touching pitch circle 224 of gear 204 and isillustrated in FIG. 3 for the right grinding wheel 209 only. Tables 206are now driven in opposing directions by their motors 217 in such amanner that they perform a rotary motion, or an angular displacement,from their initial position shown in FIG. 3 to the position shown inFIG. 4. The rotary motion of each. table 206 results in rotation,through bands 231 and 231, of each of the cylindrical rollers 229 andattached cylindrical segments 230 about their common axis. In turn, thiscauses a longitudinal shifting of each carriage 220 through the mediumof flexible bands 228 and 228' connected to opposite ends of eachcarriage.

The motion of each carriage 220, in a ratio depending on the selectedangular position of the associated rocker 221, is translated into ashifting of tool holder 208 along guide 207, and thus into an axialdisplacement of the associated grinding wheel 209 Whose edge describesan involute whose pitch diameter depends on the selected angularposition of rocker 221. Thus, it is not necessary to exchange pitchcircle roller cams in accordance with different workpieces.

While rollers 229 are illustrated as having radii less than those ofsegments 230, with correspondingly different rolling arcs, this is byway of example only, and the relative ratios of the radii and rollingarcs can be changed in accordance with the desired transmission ratio.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. In an involute gear tooth flank generating machine in which theworkpice on which an involute profile is to be shaped is heldstationary, and including a tool-holder shiftable rectilinearly along afirst elongated rectilinear guide extending parallel to the imaginarystraight rolling line of the gear, a table carrying the guide andswingable about the axis of the workpiece, the tool-holder having afirst drive member in driving connection with a stationary second drivemember coaxial with the workpiece axis, a carriage on the tableshiftable rectilinearly along a second elongated rectilinear guideextending at an angle to the first guide, a rocker on the carriagean-gularly displaceable relative to the direction of movement of thecarriage, and a slide guided for rectilinear reciprocation on the rockerand connected to the tool holder: the improvement in which said firstand second drive members are formed with cylindrical roller surfaces;flexible band means interconnecting said first and second drive members;and flexible band means connecting said first drive member to saidcarriage.

2. In an involute gear tooth flank generating machine, the improvementclaimed in claim 1, in which said flexible band means comprises a firstpair of flexible bands each connected at one end to said first drivemember and at the opposite end to said second drive member, said bandsextending in opposite angular directions around the cylindrical rollersurfaces of said first and second drive members; and a second pair offlexible bands each secured at one end to one end of said carriage andat the opposite end to said first drive member, said second bandsextending in respective opposite directions along said carriage and inrespective opposite angular directions around the cylindrical rollersurface of said first drive member.

3. In an involute gear tooth flank generating machine, the improvementclaimed in claim 1, in which said first drive member comprises a rollercylinder and a cylindrical segment secured coaxially to a common axis;said flexible band means connecting said cylindrical segment to saidsecond drive member and connecting said cylindrical roller to saidcarriage.

4. In an involute gear tooth flank generating machine, the improvementclaimed in claim 3, in which said flexible band means comprises a firstpair of flexible bands each connected at one end to said cylindricalsegment and at the opposite end to said second drive member, said firstflexible bands extending in opposite angular directions around saidcylindrical segment and around the cylindrical rolling surface of saidsecond drive member; and a pair of second bands each connected at oneend to one end of said carriage and at the opposite end to saidcylindrical roller, said second bands extending in respective oppositedirections along said carriage and in respective opposite angulardirections around said cylindrical roller.

5. In an involute gear tooth flank generating machine, the improvementclaimed in claim 3, in which the diameter of said cylindrical segmentdiflers from the diameter of said cylindrical roller.

References Cited UNITED STATES PATENTS 2,528,988 11/1950 Aeppli 51552,628,458 2/1953 Biihler 51-54 2,888,784 6/1959 Cleft 5154 X FOREIGNPATENTS 376,449 5/ 1907 France.

247,156 8/1926 Great Britain.

637,490 5/1950 Great Britain.

751,177 6/ 6 Great Britain.

ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner

